Fluid droplet recorder with a plurality of jets



March 12, 1968 W T ET AL 3,373,437

I FLUID DROPLET RECORDER WITH A PLURALITY 0F JETS Filed Aug. 1, 1967 4Sheets-Sheet l wot-:0 AMPLIFIER SYNC. 42 r m S'eEE- 44 ERATOR INVENTORS.RICHARD G. SWEET SAMPLING RAYMOND C. CUMMING PULSE GENERATOR ATTORNEY.

March 12, 1968 R. 0. SWEET ET AL FLUID DROPLET RECORDER WITH A PLURALITY0F JETS Filed Aug. 1. 1967 4 Sheets-Sheet 2 INVENTORS. RICHARD G. swAYMON EET BY R X; c. CUMMING ATTORNEY.

March 12, 1968 SWEET ET AL 3,373,437

FLUID DROPLET RECORDER WITH A PLURALITY OF JETS Filed Aug. 1, 1967 4Sheets-Sheet 5 v F I G. 4

CHARACTER MATRIX CHARACTER MATRIX TO CHARGING ELECTRODE 8 i 84 aTvEa 42?I CLOCK PULSE m sea.

86 i 88 INVENTORS. I RICHARD G. SWEET RAYMOND C. CUMMING gag; CHARACTERBY GEM SELECTOR ATTORNEY.

March 12, 1968 R. G. SWEET ET AL 3,373,437

FLUID DROPLET RECORDER WITH A PLURALITY OF JETS Filed Aug. 1, 1967 4Sheets-Sheet 4 FIG. 5

FIG.6 5

? INVENTORS. 58 RICHARD 6. SWEET RAYMOND c. CUMMING ATTORNEY.

United States Patent 3,373,437 FLUID DROPLET RECORDER WITH A PLURALITYOF JETS Richard G. Sweet, 4076 Orme Ave., and Raymond C. Cumming, 4129Donald Drive, both of Palo Alto, Calif. 94306 Continuation-impart ofapplication Ser. No. 354,721, Mar. 25, 1964. This application Aug. 1,1967, Ser. No. 660,163

16 Claims. (Cl. 346-75) ABSTRACT OF THE DISCLOSURE Signal controlledrecording apparatus having an array of jet nozzles each producing asuccession of discrete droplets of writing fluid. The droplets areelectrostatically and selectively deflected in response to signal valuesto effect either droplet deposition on a record medium or dropletinterception. The controlling signals may be programmed in accordancewith a character matrix in synchronism with the rate of dropletformation.

Cross-references to related applications This application is acontinuation-in-part of our copending application S.N. 354,721, filedMar. 25, 1964. The disclosed invention is an improvement over therecording system disclosed and claimed in the copending application ofRichard G. Sweet, S.N. 354,659, filed Mar. 25, 1964, which in turn is acontinuation-in-part of application S.N. 298,996, filed July 31, 1963(now abandoned).

Background of the invention and objects In the aforesaid copendingapplication S.N. 354,659, in the name of Richard G. Sweet, there isdisclosed a recording apparatus and method of the type in which discretedroplets of a fluid (e.g., ink) are formed and projected toward a recordmedium and electrostatically deflected in accordance with signal valuesto produce a desired graphic record. A particular feature is that thedroplets are charged in accordance with instantaneous signal values andthereafter deflected by passing them through a substantially constantelectrostatic field. The embodimentsdisclosed in said application S.N.354,659 employ a single jet nozzle with relative movement between thenozzle and the record medium. The droplets issuing from the nozzle mayproduce a line trace such as is suitable for oscillograph and othertypes of graphic recording. Various characters and images can beproduced by scanning techniques using such a single jet nozzle.

In general, it is an object of the present invention to provide arecording system utilizing the principles of said application S.N.354,659, and which is particularly adapted for presenting a displayimage as distinguished from a line trace.

Another object of the invention is to provide an apparatus and method ofthe above character which provides display type images with direct inkrecording, and which is capable of recording facsimile signals.

Another object is to provide an apparatus and method of the abovecharacter which is capable of real-time recording of standard televisionsignals.

Another object is to provide an apparatus and method of the abovecharacter which can be used for the recording of individual charactersor signals sequentially.

Another object is to provide an apparatus and method which facilitateshigh speed graphic recording of characters and images.

Additional objects and features of the invention will 3,373,437 PatentedMar. 12, 1968 "ice appear from the following description in which thepreferred embodiments have been set forth in detail in conjunction withthe accompanying drawing.

Swmmary of the invention The present apparatus and method makes use ofthe invention disclosed in said copending application S.N. 354,659,particularly in that fluid droplets from a jet nozzle areelectrostatically deflected in accordance with signal values byelectrostatically charging the droplets in accordance with instantaneoussignal values and then causing the charged droplets to be deflected bypassing them through a substantially constant electrostatic field, thedroplets being either deposited on a record medium or deflected todroplet intercepting means. The improvement herein described consists ofan array of side-by-side jet nozzles. A common fluid system supplieswriting fluid under pressure to all of the nozzles, and means isprovided for applying mechanical vibrations to the fluid in the systemwhereby varicosities are synchronously introduced into all of thestreamsissuing from the nozzles to produce uniformdiscrete droplets.Charging electrodes are provided to effect charging of the droplets of acorresponding stream in accordance with an instantaneous signal. Thesignal values can be program-med or controlled in various ways toproduce various recordings, including characters and other images. Forexample the intelligence signals applied to the charging of the dropletsmay be derived from the scanning of a piece of copy material, as inaccordance with facsimile principles; they may be derived from thescanning of material in accordance with television principles; or theymay be derived from the output of a computer logic system.

Brief description of the drawing FIGURE 1 is a perspective view ofapparatus-constructed in accordance with and illustrating the presentinvention;

FIGURE 2 is an enlarged fragmentary portion of the apparatus shown inFIGURE 1 and partly broken away to illustrate the operating principle ofthe inventive concept;

FIGURE 3 is a schematic block diagram of a portion of the electricalcircuitry useful in effecting the recording in accordance with thepersent invention;

FIGURE 4 is a series of curves illustrating the relationship of signalsat various points in the circuitry illustrated in FIGURE 3;

FIGURE 5 is a fragmentary sectional view illustrating another form ofstructure also embodying the present invention;

FIGURE 6 is an enlarged cross-sectional view of a portion of theapparatus shown in FIGURE 5; and

FIGURE 7 is a block diagram of electrical circuitry usable with theapparatus shown in FIGURES 5 and 6.

Description of the preferred embodiments Referring now to the drawing inmore detail, there is shown in FIGURES l and 2, apparatus suitable forthe recording of facsimile or video images. Ink or other suitablewriting fluid is supplied through a feed pipe 2 to a manifold 4. Themanifold 4 receives the writing fluid from the feed pipe 2 under asubstantial pressure head. A plurality of orifices 6 are provided on oneside of the manifold 4. These orifices 6 are laterally spaced along thelength of the manifold 4 and constitute a plurality of jet nozzles forthe issuance of the writing fluid from the manifold 4, under theinfluence of the pressure head, toward the surface of a record receivingmember 8. While it is presently contemplated that the preferred form ofthe invention would include a linear and uniform spacing of the orificesalong the length of the manifold 4, it will 3. be appreciated that suchuniform spatial relationship between the orifices is not essential.

As in the aforementioned copending application of Richard G. Sweet,means are provided for introducing regularly spaced varicosities in thestream of writing fluid issuing from each of the nozzles. One way inwhich this may be accomplished is by vibrating the entire manifold 4. Tothis end, a magnetostrictive driver is secured in driving relation tothe side of the manifold 4 opposite from the orifices or nozzles 6. Themagnetostrictive driver 10 includes a magnetostrictive core 12 and theassociated driving coils 14. As disclosed in the aforementioned coendingRichard G. Sweet application, when the writing fluid issues from the jetnozzles at high velocity under the influence of the pressure head, thereis a tendency for the continuous stream of writing fluid to break-upinto a succession of discrete droplet-s. This is due at least in" partto the surface tension of the writing fluid. In order to assure' thatthe droplets in each stream are uniform in dimensionand uniformlyspaced, the regularly spaced varicosities' are introduced into theissuing stream as by the vibration of the'manifold 4 at or near thenatural droplet formation frequency. Alternatively to vibrating theentire manifold 4, that wall of the manifold which engages themagnetostrictive driver may be made flexible, With the manifold fixed inposition and the one flexible wall which engages the magnetostrictivedriver 10, a high frequency pressure variation is superimposed upon thesubstantially constant high pressure head with which the writing fluidis supplied to the manifold. Such variations in pressure head producethe desired varicosities in the issuing stream.

A plurality of droplet charging electrodes 16 are provided,corresponding in number to the individual jets or issuing streams ofwriting fluid. The charging electrode 16 associated with each of theissuing streams of writing fluid embraces that stream along an area thatincludes the point at which the individual droplets separate from thecontinuous stream. The signals to be recorded are applied between themanifold 4 as one electrode, assuming, of course, that the writing fluidis electrically conductive, and selected ones of the charging electrodes16' in accordance with a selecting program as will be discussed more indetail hereafter. As the droplets in each issuing stream separate fromthe continuous stream, the individual droplets will be inductivelycharged or not charged in accordance with the potential diflerenceexisting between the common electrode or manifold and the individualcharging electrode at the instant of drop separation.

In their course between the jet nozzles and the record receiving member8, the charged droplets are caused to passbetween a pair of deflectingelectrodes 18 and 201 A constant electric field is established betweenthe deflecting electrode 18 and the deflecting electrode 20. Asillustrated, the deflecting electrode 18 is preferably connected toground potential while the deflecting electrode 20 is connected to arelatively high positive potential. Thus, if the droplets to bedeflected bear a positive charge they will be deflected toward thedeflecting electrode 18.

The spatial relationship of the elements is such that the relativelyuncharged particles are directed in a path which passes in closeproximity to the surface of the grounded deflecting electrode 18. Underthese conditions, a slight deflection of the droplets under theinfluence of the electric field established between the deflectingelectrodes and acting on the charge on the droplets, causes thedeflected droplets to impinge upon the surface of the groundeddeflecting electrode 18. The grounded electrode 18 is espeeiallyconstructed in such a manner that it not only serves as one of thedeflecting electrodes, but it also serves as the intercepting means forintercepting those droplets of writing fluid which are deflected inaccordance with the intelligence signals. Thus, the electrode 18includes, first, a hollow shell member which is formed of any suitableelectrode metal such as brass or the like. Second, there is provided acover or face member 24 for the electrode 18 which is formed of asuitable porous material. This porous material may be either aceramic-like material which may be rendered conductive as by wettingwith the writing fluid; or it may be formed of a porous sinteredpowdered metal construction which is inherently conductive. Third, thereis provided an exhaust line 26 connected to suitable exhaust pump meanswhereby the chamber defined between the hollow shell portion 1Z2 of theelectrode 18 and the porous cover portion 24' is maintained under atleast a partial vacuum. Under the influence of this partial vacuum, theink droplets which are intercepted by the electrode 18 are drawn throughthe porous cover member 24, collected in the inner chamber formedthereby, and drawn off through the exhaust line 26. Since the electrode18 also serves as the intercepting means which is connected, through theconductive writing fluid, to other elements of the system, it is readilyapparent why it is preferable. that this electrode be connected toelect'rical ground As previously mentioned, one of the uses for arecording system as just described is for the recording of video orfacsimile signals. So far as the signals to be recorded are concerned,the system for these uses may be substantially identical. FIGURE 3 isillustrative of circuit means which may be employed to effect theselective charging of the droplets of writing fluid. whereby the recordmay be produced. In both fascimile and video systems, the intelligencesignal is transmitted as a continuous train of signals. whichismodulated in accordance with the illumination of elemental imageareas. In systems compatible with commercial television, the imageintelligence is transmitted as a. succession of image fields, each fieldbeing a succession of scanned lines of information, and each line beinga succession of scanned elemental areas. In commercial television, eachfield is composed of 262 lines of information and each line consists ofa large number of area elements. A reasonable image definition may beobtained for the purpose of the present invention, if these lines areconsidered as having 315 area elements. With the television fieldsrecurring at the rate of 60' per second, the line frequency is 15,750per second. It has been noted that each line of intelligence may berepresented by 31-5 elemental areas or image segments. Accordingly, ifthe manifold 4 for the writing fluid, in accordance with the presentinvention, is provided with 315 laterally spaced orifices or jets andeach jet is provided with a corresponding charging electrode for the inkdroplets. emerging from each of said jets, and the charging electrodesare sequentially energized at the proper freqeuncy, then each scanthrough the 315 jets represents one line of the video intelligence.Successive scanning of the jets at the line scan frequency of 15,750 persecond will reproduce a reconstruction of the image from which the videointelligence signals were derived.

The circuit illustrated in FIGURE 3 is representative of means .foraccomplishing the desired scanning of the charging electrodes 16. Eachindividual charging electrode 16 is provided with a separate controlcircuit. These control circuits, however, are all connectedsimultaneously to a common source of input video intelligence signalrepresented in FIGURE 3 by the video amplifier 28. The output signalfrom the video amplifier 28 is connected to the cathode of a firstblocking diode 30 included in the control or sampling circuit for thefirst charging electrode 16. The anode of the blocking diode 30 isconnected to a junction 32. Also connected to the junction 32, through aresistor 34, is a source of positive bias potential. The junction 32 isalso connected through a. control diode 36 and a resistor 38 to anegative source of bias potential. The junction between the controldiode 36 and the resistor 38 is connected to the first chargingelectrode 16. A capacitor 49 is connected between the charging electrodeand ground. A similar control or sampling circuit is connected betweenthe video amplifier and the second of the charging electrodes 16, thecomparable elements of the second circuit bearing correspondingreferenced numerals but with a prime superscript. Similar control orsampling circuits are provided for each of the successive chargingelectrodes.

The video amplifier 23 is also connected through a suitablesynchronization circuit 42 to a sampling pulsegenerator 44. The samplingpulse generator 44 produces a series of pulses synchronized with theline scanning rate of the video signal. The scanning pulses thusproduced are applied as input signals to a progressive delay linerepresented by the series connected coils 46 and the shunt connectedcapacitors 48. To be in harmony with the commercial video signal of ourillustrative example, the total delay of the delay line is 63.5microseconds, and the delay for each successive section is 0.2microsecond. It is, of course, anticipated that with such a delay line,the sampling pulses would be progressively attenuated. To overcome theadverse effect of such attenuation, a pulse regenerator 49 is insertedat spaced interval-s along the delay line to reconstitute the pulses.Alternatively, the scanning pulses may be applied to the controlcircuits, successively, from a high speed shift register (not shown).

The delayed sampling pulse produced at the end of the first section ofthe time delay line is applied through a gating diode 50 to the junction32 in the first control or sampling circuit. The delayed pulse appearingafter the second section of the delay line is applied through a similargating diode 50' to the junction 32' of the second control or samplingcircuit. The bias signals applied to the junction 32 of the firstcontrol or sampling circuit, and the corresponding junction of thesubsequent sampling circuit is such that signals from the videoamplifier are blocked, and no signal is applied to the chargingelectrode 16. When a sampling pulse from the delay line is applied tothe gating diode 50, the bias condition at the junction 32 is changed topermit a sample pulse, representative of of the instantaneous value ofthe video signal, to be applied to the charging electrode 16. As thesampling pulses appearing at successive sections along the delay lineare applied to successive junctions 32 of the several control orsampling circuits, these circuits are gated to pass pulse signalsrepresentative of the instantaneous value of the video signal. Thus, aseach sampling pulse, initiated at .the beginning of a line scan, passesdown the delay line, the control or sampling circuits are consecutivelyturned on. The on time of'each of the sampling circuits is approximately0.2 microsecond for each scan line. The time interval between on timeperiods for each sampling circuit is approximately 63.5 mircoseconds,the time length of one line scan.

In order to provide variable shades of density of the reproduced image,that is shades of gray so-called, it is desirable that a plurality ofdroplets of writing fluid be available for each sample pulse presentedto the individual charging electrodes. For example if the parameters ofthe system are such that the drop rate frequency, that is the frequencyof the formation of the individual droplets in each jet is 63,000 persecond, four droplets will be projected from each nozzle during eachscan line interval. Proper control of these droplets will provide fourso-called shades of gray for each sampled signal. As previouslymentioned, each signal sample developed at the junction 32 of thecontrol circuit has a time duration of 0.2 microsecond. In order forcontrol to be exercised over all four of the individual droplets issuingduring each line scan cycle, each of the control or sampling circuitsincludes a pulse stretcher. The capacitor 40 in each of the control orsampling circuits constitutes the storage element of such a pulsestretcher. The R-C time constant of the circuit, aided by the diode 36,is such as to stretch the pulse to embrace the entire line scaninterval. This relationship is illustrated in FIGURE 4.

In FIGURE 4, curve A represents the intelligence portion of a typicalvideo signal where the amplitude of the wave is representative of thebrightness of the elemental area of the image. The dash line Wrepresents that value of the video intelligence signal which wouldappear as white on the reproduced image, while the dash line Brepresents the value of the video intelligence which would appear asblack on the reproduced image. Curve B represents two sample pulses eachof 0.2 microsecond duration as sampled or gated by one of the control orsampling circuits. Again, it will be noted that dash lines W and Brepresent those values of the sampled pulses which would represent,respectively, white and black values on the reproduced image. Curve Crepresents the sampled pulses as applied to the charging electrodesafter having been subjected to the pulse stretching influence of thesampling circuit.

It will be noted that the normal bias applied to the chargingelectrodes, in the absence of an applied intelligence signal, is such asto fall below the black reference line, that is all of the droplets ofwriting fluid would pass between the deflecting electrodes and impingeupon the record or paper 8. The height of the initial step in the signalapplied to the charging electrode is a function of the instantaneousmagnitude of the sampled pulse as shown in Curve B of FIGURE 4. Thisstep input or intelligence signal raises the charging potential appliedto the charging electrode 16 above the black reference line B of CurveC. This line B represents that value of the potential applied to thecharging electrodes above which the droplets of writing fluid influencedthereby will be deflected and intercepted by the deflecting electrodes18 and 20, and below which the droplets would not be deflected but beallowed to impinge upon the paper. From the peak value applied at thestep input, representing the amplitude of the sampled pulse, thepotential, as applied to the charging electrode, decays at a ratedetermined by the RC time constant of the pulse stretcher toward thebias level below the reference line B. The solid line trace of Curve Cis thus representative of the charging potential applied to one of thecharging electrodes as a result of the sampled pulses illustrated inCurve B. The first sampled pulse of Curve B extends approximatelythree-quarters of the way between the lines B and W. The correspondingsolid line curve of Curve C begins at about three-quarters of the waybetween the lines B and W of Curve C and decays toward and beyond theline B at the predetermined decay rate. The vertical dotted lines D D DD D and D of Curve C represent the recurrence of the individual inkdroplets in accordance with our illustrative example. Thus four inkdroplets are produced during the interval of each scanline. The dropletsthat occur during the interval while the solid line curve of Curve C isabove the reference line B' are all charged with a suflicient charge tocause them to be deflected and intercepted by the deflecting electrodes18 and 20. The droplets that occur during the interval while the solidline curve of Curve C is above the reference line B are all charged witha sulficient charge to cause them to be deflected and intercepted by thedeflecting electrodes 18 and 20. The droplets that occur during theinerval after the solid line curve has crossed below the reference lineB remain substantially unchanged and pass between the deflectingelectrodes and impinge upon the paper.

Referring again to our specific illustration, the sample pulse was A ofthe way between the black and white reference lines. The applied chargeto the charging electrode is such that the decay characteristic causesthe firstthree of the droplets during that scan interval to besufficiently charged to be deflected and intercepted. The remainingdroplet occurring during that scan interval is not so charged andproduces a corresponding mark on the paper. The second sample pulse isof a magnitude which reaches less than half way between the black andwhite reference line as indicated in Curve B. Referring to thecorresponding portion of Curve C it will be seen that only the firstdroplet is sufficiently charged as to be deflected and intercepted bythe deflecting electrodes 18. and 20. The remaining droplets arerelatively uncharged and do reach the paperto reduce apredominantly'dark area on. the record member; We have already mentionedthat in the absence of an. intelligence signal or if the intelligencesignal is zero at the moment of sampling all of the droplets. would bepassed by the deflecting electrodes and impinge upon the record member.The dotted line curve superimposed upon the: first portion of Curve C isrepresentative of the action that would occur if the first sample pulsehad. been of suflicient magnitude to reach the white reference line ofCurve B. It may be. seen that the dotted line curve of Curve C decays atthe same rate. as. the solid line curve. However, since it starts itsdecay from a higher level, the decaying signal does not reach the blackindex line until after all four. droplets of that scanning interval havealready been charged with a suflicient potential to cause them to bedeflected. and intercepted. Thus, if the sample pulse is of suflicientmagnitude to reach the white referenceline as shown in Curve B, then theresultant image area appearing on the record member will be acorrespondingly white area. Thus, each elemental area on the resultantimage may be. produced by the application of between 1 and 4 droplets ofwriting fluid, or, in the case of white, no droplets at all.

With a repetitionof this application of charges in succession to theplurality of jet streams of the writing fluid, and the record member 8'being advanced at an appropriate corresponding velocity, the resultantwill be a. reproduction of the image from which the video or fascimilesignals were derived.

When the recording system of the present invention is. used for thereproduction and display of individual characters, as for example, inthe case of signals derived from the output of a computer logic system,a somewhat different form of structure may be employed. Such a structureis illustrated schematically in FIGURES S and 6 of the drawing. Thisstructure is similar in some respects to that illustrated in more detailin the aforementioned copending application of Richard G. Sweet.However,. in the instant case the writing fluid issues simultaneouslyfrom a plurality of jets and the intelligence signals applied to theseveral streams of droplets cause the selected droplets in each streamto be deflected and intercepted such that the selected droplets do notreach the record member, the deflection of the droplets being solely forthe purpose of selectively intercepting a portion of the droplets inaccordance with the program or intelligence signal.

In the structure as shown in FIGURE of the instant case, a relativlyWide record member 52 is formed into a substantially semi-cylindrical,transverse configuration with the axis of the cylindrical form lyingsubstantially parallel to the direction of advancement of the recordmember. This feature is consistent with and may be accomplished by meanssuch as that illustrated in FIG- URES 7 and 8 of the aforementionedcopending application of Richard G. Sweet. Again, as disclosed in thereferenced Sweet application, the jet forming and charging members arerotatably mounted for rotation about the axis of the cylinder defined bythe record member 52. The rotating base structure which supports thedroplet formation and charging means is represented in FIGURE 5 by thedashed line circle 54. In a manner similar to that illustrated inFIGURES 1 and 2, the writing fluid is supplied to a manifold 56 under asubstantial pressure head through a feed pipe 58. The manifold isprovided with a plurality of orifices which constitute jet nozzles forthe projection of the jets of writing fluid. For the purpose ofdisplaying and printing characters, it is considered that eight suchjets are suflicient and convenient.

In the apparatus illustrated in FIGURES 1 and 2, the jets are arrangedto follow parallel paths. For the purpose of character display such asthat illustrated in FIGURES 5 and 6, it may be found convenient toarrange the jets in a converging array. Such an. arrangement permitsgreater spacing between the individual orfices and the accompanyingcharging electrodes while providing a relatively small area ofimpingements of droplet on the record member. For example, if the eightjets represent the height of the printed character, such printedcharacter may be on the order of a tenth of an inch in height on therecord member.

As before, each of the several jets is provided with a droplet chargingelectrode 60. The selection and charging of these electrodes may becontrolled as discussed in more detail hereinafter. Here again it isdesirable to produce the regularly spaced varicosities in the issuingstream of the writing fluid 8' in order to assure a measure ofuniformity in drop rate formation as well as in the drop dimension. Tothis end, a vibratory means 62 is coupled to the manifold 56. Thisvibratory means is illustrated as including a magnetostrictive drivingmember 64, an excitation winding 65, and a field core 68. Meansproviding an oscillatory driving signal is connected to the field coil68 to cause the magnetostrictive driving member 64 to, vibrate at adesired frequency, for example, at kc.

As the issuing droplets are formed by the jets, they are charged inaccordance with the programmed material by the charging electrodes 69.In the operation of. the system as here contemplated, the charges areapplied simultaneously to the selected charging electrodes and, hence,to the selected droplets. The charged droplets of Writing fluid are thenprojected between a pair of deflecting electrodes 7t) and 72. Thesedeflecting electrodes are arranged to cause the droplets to be deflectedor not deflected in accordance with the charges on the individualdroplets. The deflecting electrodes may be similar in construction tothose illustrated in FIGURES 1 and 2'. Thus, the electrode 70 mayprovide the dual function as serving as one of the electrodes of thedeflecting electrode pair as well as that of serving as the means ofintercepting the selected, deflected droplets. Thus, as the formed andcharged droplets pass between the deflecting electrodes 70 and 72, thosedroplets having the selected charged condition thereon are deflectedsufficiently out of their normal path as to impinge upon the surface ofthe intercepting electrode 70., which is provided with a permeable orporous surface. The intercepted ink droplets are drawn through theporous surface, into the chamber defined Within the structure of theelectrode 70 and carried back to a suitable reservoir by means of theexhaust line 74. As the rotating assembly 54 turns about its axis, eachstream of projected droplets scans a transverse line across the width ofthe record member. With the issuance of the droplets being projectedtoward the record member under the control of the intelligence signal,each transverse scan across the width of the record member produces aline of data symbols or character representations. Coincident with therotation of the rotating assembly, hence of the transverse scanning ofthe record member, the record member is advanced longitudinally of theaxis of rotation in such a manner that successive rotations of thewriting assembly produces successive scan lines on the record member. Itwill be appreciated that more than one writing assembly might beincluded on the rotating structure and, by proper commutation bywell-known means, provide for alternate scan lines being recorded byalternate writing assemblies. Such an arrangement would efliectivelydouble the overall writing speed of the instrumentality.

In FIGURE 7 there is shown, illustratively, one system for controllingthe energization of the charging electrodes as in FIGURES 5 and 6. Eachsymbol or character to be recorded is represented by a character matrix76 such as is illustrated in FIGURE 7. Each character matrix 76 isformed of eight horizontal or transmitting lines 73' and six vertical orcontrol lines 80. Each of the transmitting lines are connected to one ofthe charging electrodes of the writing assembly. It will be appreciatedthat a constant-amplitude pulse generator may be interposed in each ofthe transmitting lines 78 to be triggered by the signals on those lines,to supply uniform pulses to the charging electrodes. Each of thematrices is individually controlled by a shift register 82 whichenergizes the vertical or control lines in a timed sequence. The shiftregister of the matrices are controlled by pulses from a clock-pulsegenerator 84 which is operated synchronously with the droplet formation.A print-pulse generator 86 is synchronized with the clock-pulsegenerator 84 and produces a series of print pulses, at a frequencyequalling the rate at which characters are to be reproduced, which areapplied, through a character selector 88, to trigger the shift registers82 into operation to effect the energization of matrices 76. It iscontemplated that the character selector '88 may include any suitablemeans for selecting in synchronism with the print pulses, the individualcharacter to be presented to the charging electrodes, one said characterbeing presented at a time. Thus, the character selector 88 may includeany of the numerous automatic computers which may be programmed toselect individual characters in accordance with the computer logicsystem.

It will be evident from the foregoing that we have provided an apparatusand method which is an improvement to the invention of Sweet applicationS.N. 354,659. Particularly, the present invention provides adirect-writing recording system for presenting a display-type image,which image may be the result of the intelligence signals derived fromand in accordance with facsimile or television principles, or from theoutput of a computer logic system. Also it facilitates high speedoperations for recording characters and images.

We claim:

1. A direct writing recorder responsive to various signal valuescomprising, in combination, means for forming a plurality ofdiscontinuous streams of writing fluid, each stream being in the form ofa succession of discrete droplets, said plurality of streams beingarranged in a laterally displaced array; said means including amanifold, a plurality of laterally displaced orifices communicating withsaid manifold and constituting a plurality of jet nozzles for thewriting fluid, a feed pipe connected to said manifold for supplyingwriting fluid to said manifold under a substantial pressure head wherebyto cause said writing fluid to be projected from said plurality of jetnozzles toward the surface of a record receiving member for depositthereon, means for introducing regularly spaced varicosities in thestreams of said writing fluid issuing from said nozzles to assure theformation of droplets of uniform frequency and dimension; dropletintercepting means, and means for electrostatically and selectivelycharging and deflecting the droplets to effect either droplet depositionon the record medium or droplet interception by said intercepting meansin response to various signal values.

2. A recorder as in claim 1 in which the means for introducing regularlyspaced varicosities consists of means for applying mechanical vibrationto the fluid in the manifold.

3. A recorder as in claim 2 in which the means for applying mechanicalvibration superposes vibrating variations in the pressure head of thefluid within the manifold.

4. A recorder as in claim 2 in which the means for applying mechanicalvibration consists of means for vibrating one wall of the manifold.

5. A recorder as in claim 1 in which the jet nozzles are disposed in auniformly spaced lateral array.

6. A recorder as in glaim 1 in which the jet nozzles are uniformly andlaterally spaced and parallely oriented to form an array and in whichtheir intercepting means extends parallel to the array but spacedtherefrom.

7. A recorder as in claim 1 in which the jet nozzles are so disposedthat the undeflected flight pattern of the droplets toward the recordmedium is convergent.

8. A recorder as in claim 1 in which the electrostatic charging meansincludes an electrostatic electrode associated with each stream, andprogram control means for applying signal values to selected ones of theelectrodes.

9. A recorder as in claim 1 further characterized by the provision ofmeans for causing said array to be cyclically scanned transversely ofthe record receiving member.

10. A recorder as in claim 8 in which the program control means appliessignal values to selected ones of the electrodes in accordance with acharacter matrix.

11. A recorder as in claim 16 including means for applying signal valuesto selected ones of the electrodes timed to be in synchronism with therate of droplet formation.

12. Recorder apparatus of the type in which fluid droplets from a jetnozzle are electrostatically deflected in accordance with signal valuesby electrostatically charging the droplets in accordance withinstantaneous signal values and then causing the charged droplets to bedeflected by passing the-m through a substantially constantelectrostatic field, the droplets being either deposited on a recordmedium or deflected to droplet intercepting means; the improvementcomprising an array of side by side jet nozzles, a common fluid manifoldadapted to receive fluid under pressure and in communication with all ofsaid nozzles, means for applying mechanical vibration to the fluid tointroduce varicosities synchronously into all of the streams issuingfrom the nozzles to produce uniform discrete droplets, the droplets ofthe streams having the same uniform spacing and being projected insynchronism, and charging electrodes each disposed to effect charging ofthe droplets of a corresponding stream in accordance with aninstantaneous signal.

13. A recorder as in claim 12 together with means serving tomechanically scan the array of jet nozzles laterally of the recordmedium.

14. A recorder as in claim .12 together with means for causing theinstantaneous signal values to be programmed in accordance with acharacter matrix and in synchronism with the rate of droplet formation.

15. A recorder as in claim 12 in which each of said jet nozzlescorresponds to an elemental area on said record medium and in which animage having black and various shades of gray is formed, a predeterminedplurality of deposited droplets producing black and lesser numbers ofdeposited droplets producing shades of gray, said recorder includingmeans coupled to said charging electrodes to effect the deposition ofall said predetermined plurality of droplets or interception ofpredetermined fractions of said predetermined plurality of dropletswhereby a shaded image is formed.

16. A recorder as in claim 15 in which said last mentioned meansincludes a time delay circuit for determining said predeterminedfractions.

References Cited Fast Oscillograph Squirts Ink, Electronic Design, Oct.11, 1963, pp. 28-29.

RICHARD B. WILKINSON, Primary Examiner.

JOSEPH W. HARTARY, Assistant Examiner,

